This application claims priority on Japanese Patent Application No. 11-304364 filed on Oct. 26, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to chargers for use with battery packs which are used to run electric power tools. More particularly, the present invention relates to a battery pack charger with a mechanism for protecting its terminals.
2. Description of the Related Art
One type of known battery charger is encased in a housing that includes a connecting portion, such as a pair of guide rails protruding from the housing""s surface on which a battery pack is set for charging. A battery pack to be charged by such a charger typically includes a pair of slide rails on the battery pack""s surface that is set on the charger during a charge. The slide rails can be engaged with and slid along the guide rails of the charger in order to set the pack in place on the charger. When the battery pack is attached to the charger by sliding of the pack""s slide rails along the charger""s guide rails, electrical contact is established between the charge terminals and data transmission terminals provided on the connecting portion of the charger and the corresponding terminals of the battery pack.
While this type of battery charger achieves its intended objective, it is not free from certain problems and inconveniences, thus leaving room for improvement. For example, as the terminals of this charger are exposed at the connecting portion to the external environment when the battery pack is not attached to the charger, the terminals may break or otherwise suffer damage caused by the charger dropping to the floor/that may result from the charger dropping to the floor or, conversely, by an object falling onto the charger.
Although it is possible to protect the charger terminals with a terminal cover or cap that can be detached or opened manually when no battery pack is set on the charger, users are likely to consider removing and placing (or opening and closing) the cover for each charge a tedious and inconvenient task. Another problem with this arrangement is the possibility of an user inadvertently leaving the terminals uncovered and, thus unprotected, upon completion of a charge, therefore exposing the terminals of the charger to various hazards, such as the those mentioned.
In view of the above-identified problems, an important object of the present invention is to provide a battery charger wherein protection of its the terminals is ensured without requiring the user to perform any additional action, such as manually removing and replacing a protective cover on the charge, when no battery pack is set on the charger.
The above objects and other related objects are realized by the invention, which provides a charger for charging a battery pack. The charger comprises: a housing including on an outside surface thereof a connecting portion to which a battery pack is removably attached; a plurality of charger terminals provided in the connecting portion for establishing electrical connection with the battery pack upon attachment of the battery pack to the connecting portion; and protective means provided in the connecting portion, with the protective means being adapted to cover the charger terminals when the battery pack is not attached to the connecting portion and to be actuated by a motion of attaching the battery pack to the connecting portion to expose the charger terminals when the battery pack is attached to the connecting portion.
When the battery pack is not set on the charger, the protective means ensures protection of the terminals of the charger from falling objects or from damage to the terminals caused by the charger falling to the floor or the ground. Further, the protective means is actuated by attachment of the battery pack to the charger to expose the charger""s terminals, and the protective means is adapted to automatically return to the protruding position upon removal of the battery pack from the charger. This ensures protection of the terminals without requiring additional action by the user whenever the battery pack is removed from the charger. Unlike with a detachable protective means, such as a detachable cover, there is no possibility of inadvertently leaving the charger terminals uncovered upon completion of a charge.
According to one aspect of the present invention, the protective means comprises a rotatable cover adapted to rotate between a protruding position, which is attained when the battery pack is not attached to the connecting portion, in which at least a portion of the cover protrudes from the housing and the connection portion so as to at least partially cover the charger terminals, and a retracted position, which is attained when the battery pack is attached to the connecting portion, in which the cover is at least partially retracted inside the housing. The rotatable cover provides suitable protective means for use with a structure in which a battery pack is slid on the charger into attachment therewith.
According to another aspect of the present invention, the charger further comprises guide means provided in the connecting portion for allowing the battery pack to be slid along a predetermined guide locus into attachment to the connecting portion and biasing means for urging the protective cover to the protruding position when the battery pack is not attached to the connecting portion. In this structure, the battery pack is brought into contact with and rotate the protective cover to the retracted position against the biasing force of the biasing means when the pack is slid along the guide locus.
According to another aspect of the present invention, the guide locus has a front end at which a front portion of the battery pack is placed on the charger prior to sliding of the charger into attachment with the connecting portion and a rear end to which the battery pack is slid into attachment with the connecting portion, and the protective cover is pivotally disposed between the front and rear ends of the guide locus so as to pivot toward the rear end to the retracted position when the battery pack is slid to the rear end of the guide locus.
According to still another aspect of the present invention, the protective cover includes a transverse top plate extending substantially orthogonal to the guide locus, a pair of vertical side plates connected to the top plate, and a pair of pivots for supporting the side plates inside the housing so as to allow the protective cover to pivot along the guide locus between said two positions, the top plate being located outside the housing directly above the charger terminals to protectively cover the charger terminals when the battery pack is not attached to the connecting portion.
According to still another aspect of the present invention, the charger further includes a transverse slit formed in the connecting portion for allowing the top plate to pivot between the two positions and a pair of side slits provided in the connecting portion for allowing the side plates to pivot between the two positions.
According to yet another aspect of the present invention, the top plate has a curved cross section on a plane parallel to the guide locus, with the curvature of the section substantially coinciding with the locus of the pivoting motion of the top plate. In addition, the transverse slit is at least partially defined by at least one wall surface of the housing having a curvature substantially concentric with said locus of the pivoting motion.
According to one feature of the present invention, the guide means and the guide locus are slanted such that the rear end of the guide locus is located at a lower level than the front end, facilitating sliding and thus attachment of the battery pack to the connecting portion.
According to another feature of the present invention, the guide means includes a pair of guide rails for slidably engaging the battery pack, whereas the biasing means includes a coil spring fitted on one of the side plates.
In one embodiment, the protective means includes a pair of rotatable covers, with the charger further including guide means provided in the connecting portion for allowing the battery pack to slide along a guide locus into attachment to the connecting portion. The charger further includes biasing means for urging the rotatable covers to respective protruding positions, which are attained when the battery pack is not attached to the connecting portion, in which at least a portion of each rotatable cover protrudes out of the housing and the connection portion so as to cover the charger terminals. Additionally included in the charger is a button located in the guide locus and depressed by the battery pack when the pack is placed on the connecting portion prior to sliding of the battery pack on the charger into attachment to the connecting portion. When depressed by the battery pack, the button actuates the rotatable covers to rotate against the biasing force of the biasing means from the respective protruding positions to respective retracted positions, in which the covers are retracted inside the housing so as to expose the charger terminals. Provision of two protective, rotatable covers provide even greater protection for the terminals than a single cover does.
According to still another feature of the present invention, the guide locus has a front end at which a front portion of the battery pack is placed on the charger prior to sliding of the charger into attachment with the connecting portion and a rear end to which the battery pack is slid into attachment with the connecting portion. Moreover, the rotatable covers are pivotally disposed between the front and rear ends of the guide locus and the button is located between the front end and the rotatable covers.
According to yet another feature of the present invention, the button extends through the connecting portion and is adapted to be depressed by the weight of the battery pack to actuate the rotatable covers to rotate to the respective retracted positions when the pack is placed on the button.
In accordance with one aspect of the present invention, the rotatable covers are pivotally supported inside the housing by a common pivot extending parallel to the guide locus and are substantially symmetrical about a plane passing through the common pivot so as to pivot away from each other in directions orthogonal to the guide locus when the button is depressed, and wherein opposing continuous edges of the covers abut each other on said plane passing through the common pivot when the two covers are in the respective protruding positions so as to completely cover the charger terminals outside the housing.
In accordance with another aspect of the present invention, each cover includes a curved top plate having an identical arc-shaped cross section on a plane orthogonal to the guide locus and a pair of vertical side plates connected to the top plate such that when the covers abut each other in the protruding positions, said cross sections of the top plates form a continuous arc.
In still another aspect, the biasing means includes a coil spring fitted on the rotatable covers, whereas the guide means includes a pair of guide rails for slidably engaging the battery pack.
In yet another aspect, the housing includes a plurality of slits provided therein to permit the covers to rotate between the respective protruding positions and the respective retracted positions.
Other general and more specific objects of the invention will in part be obvious and will in part be evident from the drawings and descriptions which follow.